Bipolar Intramuscular Electrodes Research Articles

P086 The insomnia severity index is related to the respiratory arousal threshold in people with Co-Morbid Insomnia and Sleep Apnoea (COMISA)

Abstract Introduction People with co-morbid insomnia and sleep apnoea (COMISA) have worse symptoms and require a tailored therapy approach for their sleep disorders. The relationship between the respiratory arousal threshold, a key OSA non-anatomical contributor and insomnia symptoms is unclear. This study investigated the relationship between insomnia symptoms using the insomnia severity index (ISI) and the respiratory arousal threshold in people with OSA. Methods 46 people with OSA (11 female, age=50±15years, BMI=29±6kgm-2, AHI=33±20events/h) participated in a physiology sleep study to predict response to oral appliance therapy and completed the ISI. Standard polysomnography, an epiglottic airway pressure sensor, bipolar intramuscular electrodes inserted into the genioglossus and a nasal mask with a pneumotachograph to quantify airflow were used. The respiratory arousal threshold was measured as the nadir epiglottic pressure during a respiratory event prior to a cortical arousal. Following this, participants trialled mandibular advancement therapy. Results There was no relationship between ISI (average=12±6) and the arousal threshold (-24±10cmH₂O) in participants with OSA (r=0.1, p=0.42, n=46). However, in the 59% of people with COMISA (ISI ≥11), there was a positive relationship between ISI and arousal threshold, with increasing insomnia severity associated with lower arousal threshold (r=0.5, p=0.017, n=27). People with a BMI<30kgm-2 (n=27), also had a positive linear relationship between ISI and improvement in oral appliance therapy (r=0.49, p<0.01, n=27). Conclusion Greater insomnia symptoms in people with COMISA is associated with a lower respiratory arousal threshold. In non-obese people with OSA, higher ISI values are related to poor response to oral appliance therapy.

SY5.4. Monitoring for peripheral nerve surgery

Injuries or diseases of peripheral nerves can have severe impact on function, severe disability (inability to work), social and psychological effects or chronic pain. The main reason to perform Intraoperative monitoring (IOM) during peripheral nerve surgery are to prevent nerve injuries during surgery, to identify peripheral nerves or fascicles in cases of variable anatomy, scar tissue or tumors, to determine axon continuity across a lesion, and to guide surgical decisions regarding the type of neural reconstruction to perform. Nerve action potential (NAP) recording is considered a standard method for peripheral nerve monitoring given its ability to determine the presence or absence of functional axons in a segment of nerve, it also localizes functional and non-functional nerve segments. A NAP recording requires 4.000 to 5.000 intact or regenerating axons to be obtained and its preferred to compound muscle action potential (CMAP) recordings. The presence or absence of a NAP is more important than its latency, amplitude or shape. If a NAP is recorded in a nerve or fascicle, neurolysis is performed, and nerve grafts are required in no-responding fascicles. Some technical difficulties of NAP recording are related to very short stimulation/recording distances, stimulus artifact, volume conduction from another nerve, low temperature, use of tourniquet and use of local anesthetics. CMAP recording is like that used in triggered EMG, surface or subcutaneous needle electrodes are placed over desired muscles and the exposed peripheral nerve is stimulated. Free EMG is useful to detect, in real time, trains or bursts of abnormal discharges that indicate possible nerve damage. It́s easy to use, not affected by anesthesia and has high sensitivity but low specificity. Bipolar intramuscular electrodes are preferred for EMG recordings.

Stable, simultaneous and proportional 4-DoF prosthetic hand control via synergy-inspired linear interpolation: a case series

BackgroundCurrent commercial prosthetic hand controllers limit patients’ ability to fully engage high Degree-of-Freedom (DoF) prosthetic hands. Available feedforward controllers rely on large training data sets for controller setup and a need for recalibration upon prosthesis donning. Recently, an intuitive, proportional, simultaneous, regression-based 3-DoF controller remained stable for several months without retraining by combining chronically implanted electromyography (ciEMG) electrodes with a K-Nearest-Neighbor (KNN) mapping technique. The training dataset requirements for simultaneous KNN controllers increase exponentially with DoF, limiting the realistic development of KNN controllers in more than three DoF. We hypothesize that a controller combining linear interpolation, the muscle synergy framework, and a sufficient number of ciEMG channels (at least two per DoF), can allow stable, high-DoF control.MethodsTwo trans-radial amputee subjects, S6 and S8, were implanted with percutaneously interfaced bipolar intramuscular electrodes. At the time of the study, S6 and S8 had 6 and 8 bipolar EMG electrodes, respectively. A Virtual Reality (VR) system guided users through single and paired training movements in one 3-DoF and four different 4-DoF cases. A linear model of user activity was built by partitioning EMG feature space into regions bounded by vectors of steady state movement EMG patterns. The controller evaluated online EMG signals by linearly interpolating the movement class labels for surrounding trained EMG movements. This yields a simultaneous, continuous, intuitive, and proportional controller. Controllers were evaluated in 3-DoF and 4-DoF through a target-matching task in which subjects controlled a virtual hand to match 80 targets spanning the available movement space. Match Percentage, Time-To-Target, and Path Efficiency were evaluated over a 10-month period based on subject availability.Results and conclusionsIn 3-DoF, S6 and S8 matched most targets and demonstrated stable control after 8 and 10 months, respectively. In 4-DoF, both subjects initially found two of four 4-DoF controllers usable, matching most targets. S8 4-DoF controllers were stable, and showed improving trends over 7–9 months without retraining or at-home practice. S6 4-DoF controllers were unstable after 7 months without retraining. These results indicate that the performance of the controller proposed in this study may remain stable, or even improve, provided initial viability and a sufficient number of EMG channels. Overall, this study demonstrates a controller capable of stable, simultaneous, proportional, intuitive, and continuous control in 3-DoF for up to ten months and in 4-DoF for up to nine months without retraining or at-home use with minimal training times.

Stable, three degree-of-freedom myoelectric prosthetic control via chronic bipolar intramuscular electrodes: a case study

BackgroundModern prosthetic hands are typically controlled using skin surface electromyographic signals (EMG) from remaining muscles in the residual limb. However, surface electrode performance is limited by changes in skin impedance over time, day-to-day variations in electrode placement, and relative motion between the electrodes and underlying muscles during movement: these limitations require frequent retraining of controllers. In the presented study, we used chronically implanted intramuscular electrodes to minimize these effects and thus create a more robust prosthetic controller.MethodsA study participant with a transradial amputation was chronically implanted with 8 intramuscular EMG electrodes. A K Nearest Neighbor (KNN) regression velocity controller was trained to predict intended joint movement direction using EMG data collected during a single training session. The resulting KNN was evaluated over 12 weeks and in multiple arm posture configurations, with the participant controlling a 3 Degree-of-Freedom (DOF) virtual reality (VR) hand to match target VR hand postures. The performance of this EMG-based controller was compared to a position-based controller that used movement measured from the participant’s opposite (intact) hand. Surface EMG was also collected for signal quality comparisons.ResultsSignals from the implanted intramuscular electrodes exhibited less crosstalk between the various channels and had a higher Signal-to-Noise Ratio than surface electrode signals. The performance of the intramuscular EMG-based KNN controller in the VR control task showed no degradation over time, and was stable over the 6 different arm postures. Both the EMG-based KNN controller and the intact hand-based controller had 100% hand posture matching success rates, but the intact hand-based controller was slightly superior in regards to speed (trial time used) and directness of the VR hand control (path efficiency).ConclusionsChronically implanted intramuscular electrodes provide negligible crosstalk, high SNR, and substantial VR control performance, including the ability to use a fixed controller over 12 weeks and under different arm positions. This approach can thus be a highly effective platform for advanced, multi-DOF prosthetic control.

Closed-Loop Continuous Hand Control via Chronic Recording of Regenerative Peripheral Nerve Interfaces.

Loss of the upper limb imposes a devastating interruption to everyday life. Full restoration of natural arm control requires the ability to simultaneously control multiple degrees of freedom of the prosthetic arm and maintain that control over an extended period of time. Current clinically available myoelectric prostheses do not provide simultaneous control or consistency for transradial amputees. To address this issue, we have implemented a standard Kalman filter for continuous hand control using intramuscular electromyography (EMG) from both regenerative peripheral nerve interfaces (RPNI) and an intact muscle within non-human primates. Seven RPNIs and one intact muscle were implanted with indwelling bipolar intramuscular electrodes in two rhesus macaques. Following recuperations, function-specific EMG signals were recorded and then fed through the Kalman filter during a hand-movement behavioral task to continuously predict the monkey's finger position. We were able to reconstruct continuous finger movement offline with an average correlation of and a root mean squared error (RMSE) of 0.12 between actual and predicted position from two macaques. This finger movement prediction was also performed in real time to enable closed-loop neural control of a virtual hand. Compared with physical hand control, neural control performance was slightly slower but maintained an average target hit success rate of 96.70%. Recalibration longevity measurements maintained consistent average correlation over time but had a significant change in RMSE ( ). Additionally, extracted single units varied in amplitude by a factor of +18.65% and -25.85% compared with its mean. This is the first demonstration of chronic indwelling electrodes being used for continuous position control via the Kalman filter. Combining these analyses with our novel peripheral nerve interface, we believe that this demonstrates an important step in providing patients with more naturalistic control of their prosthetic limbs.

26. Mapping of the cauda equina with free running and provoked EMG

Although intraoperative damage to nerve roots it’s not as catastrophic as spinal cord injuries, damage to these structures could produce motor and sensory deficit, neuropathic pain, bladder and bowel dysfunction. Free-running EMG is considered a standard method for root monitoring given its ability to detect, in real time, trains or bursts of abnormal discharges that indicate possible ventral root damage. It’s easy to use, not affected by anesthesia and has high sensitivity but low specificity. Given the myotomal overlapping multichannel recordings are required using preferably bipolar intramuscular electrodes. Triggered electromyography (tEMG) allows the surgeon to map viable neural tissue and to detect the proximity of instrumentation to nerve roots. tEMG has also been used as guidance during selective dorsal rhizotomy and it helps in the safe placement of pedicle screws. Bipolar stimulation is more selective and allows better spatial discrimination, a threshold higher than 6–8 mA (using a pulse duration of 0.1 ms) indicates very likely absence of functional tissue. Both methods have important limitations and should not be used alone but as a part of a multimodality monitoring plan including also somatosensory evoked potentials, transcranial electrical motor evoked potentials, H and sacral reflexes.

Tibialis posterior EMG activity during barefoot walking in people with neutral foot posture

The aim of this study was to characterize the electromyographic (EMG) profile of tibialis posterior during barefoot walking in order to establish a reference database for neutral foot posture. Fifteen participants had their foot posture screened using the six-item Foot Posture Index. Bipolar intramuscular electrodes were inserted into tibialis posterior and peroneus longus utilizing ultrasound guidance. Surface electrodes were placed over medial gastrocnemius, peroneus brevis and tibialis anterior. EMG and footswitch gait characteristics were recorded whilst participants completed 10 barefoot walking trials. Individual and grand ensemble averages were used to characterize the intensity profiles for each muscle. Results indicated that for most of the participants, tibialis posterior displayed two bursts of EMG activity, with the first burst during the initial contact phase and the second burst during midstance. However, there was significant variability between participants. The grand ensemble average for tibialis posterior was comparable to peroneus longus which displayed similar temporal and intensity characteristics. It is suggested that this may reflect a synergistic relationship between these muscles during stance phase, although this was not consistent for all participants. Further research is required to determine if this relationship is altered in abnormal foot posture and whether it is clinically important. In conclusion, the EMG profile of tibialis posterior during the gait cycle appeared to be highly variable among participants. However, the authors believe that EMG findings from the participants with neutral foot posture in this study may be used for comparison to EMG patterns in people with abnormal foot posture and individuals affected by musculoskeletal disease.

A pilot study of the initial effects of anti-pronation taping on electromyographic activity of lower leg muscles during walking

Clinicians frequently use anti-pronation (AP) taping to relieve symptoms and improve function in the management of musculoskeletal pain and injury, yet the mechanisms behind this effect have not been fully explored. To date, the majority of the literature has focused on the mechanical effects of AP taping and little has been done to explore its possible neurophysiological effects. This pilot study set out to investigate the effect of the Augmented LowDye taping technique on the electromyographic (EMG) activity of muscles of the lower leg during walking. Five asymptomatic subjects, who exhibited clinically abnormal pronation during a visual assessment of gait, walked on a treadmill for ten minutes before and after the application of the taping technique. Bipolar intra-muscular electrodes were used to record the EMG of the tibialis anterior (TA), tibialis posterior (TP), gastrocnemius (GN) and peroneus longus (PL) during walking. A two-way repeated measures analysis of variance was used to compare the EMG activity (peak amplitudes, duration of activity) for each muscle. The co-efficient of multiple correlations was calculated to evaluate the variability of muscle recruitment patterns within each subject. Visual comparisons of EMG activity during individual walking strides before and after the application of tape were also performed. Peak EMG activity decreased by 25% in TA and by 45% in TP following the application of tape. There were no significant differences in peak EMG activity of GN or PL, or in duration of EMG activity for any muscle. Results from this study suggest that neurophysiological changes could contribute to the mechanism behind AP taping.

The Electromyographic Activity of Thoracic Paraspinal Muscles Identified as Abnormal With Palpation

Objective The aim of this study was to compare the electromyographic (EMG) activity of deep muscles in the thoracic paravertebral gutter (PVG) detected as abnormal to palpation (AbPT) and reported as tender by the subject with muscles underlying nontender (NT), normal to palpation sites under various experimental conditions. Methods Twelve subjects (mean age, 25.42 years; range, 22-43 years) participated in this study. Fine-wire, bipolar intramuscular electrodes were inserted, under real-time ultrasonic guidance, into the deep paravertebral muscle mass underlying 1 AbPT and 2 NT sites (1 segment above and below the AbPT site) in the thoracic PVG regions. Electromyographic activity was recorded under the following conditions: resting prone, prone active trunk extension, application of pressure (300 kPa) to adjacent spinous processes, resting seated, passive and active seated trunk rotation, and supporting 2-kg weights in outstretched arms. Results Mean EMG activity was highest at the AbPT site, relative to NT sites, under all conditions, with a significant between-group effect of site ( F 2,31 = 4.13, P = .03) and large between-group effect size (η 2 = 0.21). There was also a trend for lower percentage change from baseline resting at the AbPT sites, relative to the NT sites, in response to the demand of other conditions. There were large variations in EMG activity within and between individuals, and large SDs accompanied the mean values of EMG activity in all cases. Conclusion Increased motor activity may be a contributing factor to tissue changes in the PVG detected with palpation. However, caution must be used when interpreting these results because of the large variations, small sample size, and issues associated with EMG normalization.

The electromyographic activity of thoracic paraspinal muscles identified as abnormal with palpation

Introduction Early osteopathic research is often quoted to support the proposal of paraspinal muscle overactivity associated with intervertebral dysfunction, 1,2 but these studies are dated and lack valid analysis. 3 The aim of this study was to compare the EMG activity of deep muscles in the thoracic paravertebral gutter (PVG), detected as abnormal to palpation (AbPT) and reported as tender by the subject, with muscles underlying non-tender, normal to palpation (NT) sites. Methods Fine-wire, bi-polar intramuscular electrodes were inserted, under real-time ultrasonic guidance, into the deep paravertebral muscle mass underlying one AbPT and two NT sites (one segment above and below the AbPT site) in the thoracic PVG regions of 12 healthy subjects (mean age=25.42 years, range=22–43 years). EMG activity was recorded under the following conditions: resting prone, prone active trunk extension, application of pressure (300kPa) to adjacent spinous processes, resting seated, passive and active seated trunk rotation, and supporting 2kg weights in outstretched arms. EMG values were normalised to the mean peak amplitude at each site obtained under any of the conditions. Results There was a trend for increased normalised EMG activity at the AbPT site, relative to NT sites, with a significant difference between the AbPT and NT sites under the condition of resting seated ( F 2,31 =03.56, P =0.04), and medium and large effect sizes were calculated for many of the conditions. There was also a trend for a lower percentage change from baseline resting at the AbPT sites, relative to the NT sites, under the demands of other conditions. There were large variations in normalised EMG activity within and between individuals, and large standard deviations accompanied the means of EMG activity in all cases. Conclusion The findings of this study suggest that increased motor activity may be a contributing factor to tissue changes in the PVG detected with palpation, but caution must be used when interpreting these results due to the large variations and small sample size.

Electromyographic characteristics of deep, thoracic paraspinal musculature

Introduction Few researchers have examined the recruitment and activation patterns of deep, thoracic paraspinal muscles. Raw EMG signals from intra-muscular electrodes from different sites within the same muscle are highly variable in magnitude, 1 making direct comparison of raw, fine-wire EMG data from multiple thoracic sites invalid. To overcome this problem, EMG data should be normalised using maximal voluntary contraction (MVC), but the best method for eliciting MVC in deep, thoracic paraspinal muscles is unknown. Design Single cohort, repeated measures design. Methods Fine-wire, bi-polar intramuscular electrodes were inserted, under real-time ultrasonic guidance, into the deep paravertebral muscle mass underlying three adjacent sites in the thoracic PVG regions of 12 subjects (mean age=25.42 years, range=22–43). EMG activity was recorded under passive and active conditions. Two tasks, active prone extension and holding weights (2kg) in outstretched arms, were expected to elicit MVC. Results There were large variations in EMG activity within and between individuals. Peak amplitudes for individual sites were found under every condition, except resting prone. There was a significant difference between activity under the different conditions ( F 3.1,102.3 =0.04). The lowest mean EMG activity occurred during resting prone (0.11mV, SD=0.12), and the highest mean activity was recorded for passive rotation to the opposite side (0.51mV, SD=0.70). The mean amplitude for holding weights (0.42mV, SD=0.76) was higher than for active thoracic extension (0.34mV, SD=0.48), and there was a weak, inverse correlation ( r =−0.23) between the mean values recorded from these tasks. Conclusions EMG activity from deep, thoracic paraspinal muscles was highly variable, and no single task elicited MVC from all sites. The highest EMG activity occurred during passive rotation to the opposite side, which may be related to the proposed role of these muscles as spinal stabilisers. Active extension and holding weights in outstretched arms appeared to activate the muscles in different ways. EMG values should be normalised to the peak amplitude of each site.

Shoulder musculature activation during upper extremity weight-bearing exercise.

Repeated-measures design comparing 7 static weight-bearing shoulder exercises. The purpose of this study was to determine the demand on shoulder musculature during weight-bearing exercises and the relationship between increasing weight-bearing posture and shoulder muscle activation. Weight-bearing shoulder exercises are commonly prescribed in the rehabilitation of shoulder injuries. Limited information is available as to the demands placed on shoulder musculature while these exercises are performed. Eighteen healthy college students volunteered for this study. Surface bipolar electrodes were applied over the infraspinatus, posterior deltoid, anterior deltoid, and pectoralis major muscles. Fine-wire bipolar intramuscular electrodes were inserted into the supraspinatus muscle. Electromyographic (EMG) root mean square signal intensity was normalized to 1 second of EMG obtained with a maximal voluntary isometric contraction (MVIC). Subjects were tested under 7 isometric exercise positions that progressively increased upper extremity weight-bearing posture. There was a high correlation between increasing weight-bearing posture and muscular activity (r = 0.97, P < 0.01). There was relatively little demand on the shoulder musculature for the prayer and quadruped positions (2%-10% MVIC). Muscular activation was greater for the infraspinatus than for other shoulder muscles throughout most of the exercise positions tested. These results indicate that alterations of weight-bearing exercises, by varying the amount of arm support and force, resulted in very different demands on the shoulder musculature. Specifically, the infraspinatus was particularly active during the weight-bearing exercises used in this study.

Modelling the masticatory biomechanics of a pig.

The relationships between muscle tensions, jaw motions, bite and joint forces, and craniofacial morphology are not fully understood. Three-dimensional (3-D) computer models are able to combine anatomical and functional data to examine these complex relationships. In this paper we describe the construction of a 3-D dynamic model using the anatomical (skeletal and muscle form) and the functional (muscle activation patterns) features of an individual pig. It is hypothesized that the model would produce functional jaw movements similar to those recordable in vivo. Anatomical data were obtained by CT scanning (skeletal elements) and MR imaging (muscles). Functional data (muscle activities) of the same animal were obtained during chewing by bipolar intramuscular electrodes in six masticatory muscles and combined with previously published EMG data. The model was driven by the functional data to predict the jaw motions and forces within the masticatory system. The study showed that it is feasible to reconstruct the complex 3-D gross anatomy of an individual's masticatory system in vivo. Anatomical data derived from the 3-D reconstructions were in agreement with published standards. The model produced jaw motions, alternating in chewing side, typical for the pig. The amplitude of the jaw excursions and the timing of the different phases within the chewing cycle were also in agreement with previously published data. Condylar motions and forces were within expected ranges. The study indicates that key parameters of the pig's chewing cycle can be simulated by combining general biomechanical principles, individual-specific data and a dynamic modelling approach frequently used in mechanical engineering.

The reliability of monopolar and bipolar fine-wire electromyographic measurement of muscle fatigue.

Bipolar intramuscular wire electrodes and spectral analysis of the electromyographic signal have been used to measure fatigue in muscles that cannot be studied with surface electrodes. Intramuscular electrodes can detect a greater range of frequencies from muscle, obtain a less distorted signal, and are therefore felt to be more sensitive to detecting fatigue. To determine the reliability and sensitivity of electrode placement (with a fixed distance) for assessing muscle fatigue, we placed three intramuscular electrodes in and two surface electrodes on the biceps brachii of 30 healthy male subjects. With these electrodes, we devised eight configurations that were analyzed separately for reliability. Subjects performed four, 30-s isometric fatiguing contractions divided between two testing sessions. Mean and median frequency of the power density spectrum were plotted against time. Linear regression was performed to obtain slopes, which were used as indicators of fatigue. The bipolar surface electrode configuration displayed mean and median frequency intrasession and mean frequency intersession reliability for slope. All four bipolar fine-wire configurations had mean and median frequency intrasession reliability (P < or 0.05). Only three of the four bipolar fine-wire configurations approached mean frequency intersession reliability, and none fo the four displayed median frequency intersession reliability. the configuration with distal bipolar intramuscular electrodes placed 1 cm apart was the most reliable intramuscular technique. The bipolar fine-wire configuration studied showed a trend toward better reliability than monopolar fine-wire configurations. No intramuscular technique, however, was reliable enough for clinical use in the study of fatigue.

An electromyographic analysis of the temporalis function of normal occlusion

Electromyographic (EMG) activity was recorded from the anterior, middle, and posterior regions of the temporalis muscle in ten subjects with normal occlusion of the teeth and with the mandible at rest and during exertion of increased biting force, using bipolar intramuscular electrodes. Results show that the posterior part of the temporalis muscle maintains the mandibular posture. Although there is no statistically significant difference in EMG recordings between the three divisions of the temporalis muscle during intercuspal biting, individual variations in EMG pattern exist. During exertion of increased biting force the EMG activity increases proportionally in all parts of the muscle. During retruded biting force the posterior temporalis predominates. The EMG activity of the temporalis muscle is correlated to the form and position of the mandible.